1. Field of the Invention
The present invention relates to novel polyamino acid derivatives. More specifically, the present invention relates to novel polyamino acid derivatives which are useful as a chelating agent for metallic ions such as Ca, Mg, Fe or Cu. The present invention further relates to the use of polyamino acid derivatives, inclusive of such novel polyamino acid derivatives, as 1) a pigment dispersant for paints or inks, 2) a surface-treating agent for a powder used in paints, inks, resin composite materials or toiletries, 3) a humectant in toiletries, or 4) a rust-proofing agent.
2. Discussion of the Background Art
Polyamino acid derivatives obtained by condensing amino acids or derivatives thereof through heat polymerization in such that the amino acids or derivatives thereof are bound through the peptide linkage, have been so far known. For example, polyaspartates have been used as a humectant in toiletries.
An amino acid itself contains both a carboxyl group and an amino group in the molecule, having ampholytic properties. However, since amino acids are bound, as just described, through the peptide linkage in a polyamino acid known so far, properties inherent in amino acids, for example, ampholytic properties, have been lost.
Meanwhile, it is disclosed in JP-A-9-194448 that amino acid derivatives (diamine-type polyamino acids) in which two molecules of an amino acid are bound to one molecule of a dihaloalkane or epichlorohydrin are useful as a highly biodegradable chelating agent. Further, it is disclosed in U.S. Pat. No. 3,989,636 that a copolymer of glycine or aspartic acid and epichlorohydrin (degree of polymerization n=2 to 3) has a chelating activity.
Thus, those compounds in which two or three amino acid molecules are bound through other than the peptide linkage are indeed known, but no higher-molecular compounds have actually produced and examined upon the properties thereof. And, none of the polyamino acid derivatives already known have been applied as any agents other than the chelating agent.